Impact of Watermelon bud necrosis virus (WBNV) infected plants on the volatile emission pattern in cowpea plants

Pathogens, including tospoviruses, are known to manipulate the behaviour of vectors after virus acquisition by plants to enhance virus transmission. Furthermore, as recently proven in the maize chlorotic mottle virus pathosystem, the vector's choice for virus-infected plants can change to a preference for noninfected plants after virus uptake by the vector. A similar trend was observed in the cowpea - Watermelon Bud Necrosis Virus (WBNV) - Thrips palmi (Karny) pathosystem. Similarly, in the no-choice bioassay, viruliferous T.palmi (carrying WBNV) settled preferentially more on healthy cowpea plants (56%) compared to virus-infected plants (47.3%), whereas non-viruliferous T.palmi settled preferentially more on WBNV infected (58.67%) cowpea plants compared to healthy plants (44%). The changes in preference of thrips towards host plants before and after virus acquisition may be due to the change of volatile cues. This study looked at the headspace volatile composition of healthy and WBNV-infected cowpea plants that attract thrips. Furthermore, the volatile analysis revealed that 1, 2-Propanediamine (0.62%) and Tuaminoheptane (0.55%) from healthy cowpea plants, as well as Tetradecane (0.35%) from WBNV-infected cowpea plants, both have a higher area percent than other volatiles. The amine (53%) and hydrocarbon (69%) groups of volatile organic compounds make up the majority of host volatiles found in healthy and virus-infected plants. The increased contact rates of viruliferous and non-viruliferous T.palmi towards healthy and WBNV-infected host plants could enhance virus transmission if thrips feed on them and acquire the pathogen prior to dispersal and the recorded host volatiles might be useful in vector management in future

Deterrence of Shoot and Capsule Borer Conogethes Punctiferalis Guenee and Thrips Sciothrips Cardamomi Ramk. of Small Cardamom by Certain Neem Formulations

Keywords: Thrips, Conogethes punctiferalis Guenee, Cardamom, Shoot and capsule borer, Sciothrips cardamomi Ramk

Preference shifts in Bemisia tabaci (Aleyirodidae: Hemiptera) after the acquisition of mungbean yellow mosaic virus from Vigna radiata

The silver leaf whitefly, Bemisia tabaci (Aleyrodidae: Hemiptera), is a polyphagous pest and a major vector of plant viruses, causing significant economic losses globally. It exhibits a complex of cryptic species and is known to transmit various plant viruses affecting numerous crops globally. A study was conducted in Tamil Nadu, India, to identify the dominant cryptic species of B. tabaci on legume crops, leading to the establishment of laboratory colonies of the most common types. The research focused on the feeding preferences of these whiteflies on healthy green gram plants (Vigna radiata (L.) R. Wilczek) versus those infected with the Mungbean Yellow Mosaic Virus (MYMV). Biochemical changes in MYMV-infected green gram plants, compared to healthy ones, were analysed to understand their influence on whitefly feeding preference. The cryptic species Asia II 8 was found to be the most common in legume crops. The study assessed whether these whiteflies favoured healthy green gram plants or those infected with MYMV. Our findings revealed that when healthy whiteflies acquired the virus from the host, their preference shifted toward healthy plants. This shift is linked to the biochemical changes associated with the infection status of the host. Following viral infection, there was a decrease in total sugars and chlorophyll, while levels of protein, phenol, peroxidase, and polyphenol peroxidase increased. These results suggest that the virus modifies the vector\u27s behaviour through a shared host, enhancing the pathogen\u27s ability to disseminate within the ecosystem

Field screening of greengram (Vigna radiata L.) genotypes for resistance against Urdbean Leaf Crinkle Virus

In the current study one hundred and seven greengram genotypes screened at Department of Pulses, TNAU, Coimbatore using AICRP pest susceptibility scale. It was observed that RME-16-3, RME-16-12, MLT-GG R-16-007, MLT-GG R-16-009, COGG 1319 (rabi-greengram) were highly resistant (HR) to Urdbean Leaf Crinkle Virus (ULCV). None of the greengram genotype is highly resistant in kharif season. Resistance in each case were associated with lower incidence, lower spread and milder symptoms relative to the susceptible cultivars. KEM 16-1, KEM 16-8, KEM 16-20, KME -33, MLT- GG K-16-01, MLT- GG K-16-05 (kharif-greengram) and RME-16-10, MLT-GG R-16-008 (rabi-greengram) were highly susceptible (HS). In susceptible cultivars of greengram, the disease is characterized by enlargement of trifoliate leaves and crinkling of the leaf lamina. However, severity of the symptoms varies in different cultivars. Early infected greengram plants showed complete sterility. The affected plants become stunted and gave a bushy appearance and no pods were formed in severely affected plants. Better understanding of resistance of genotypes will help in improvement of varieties resistant to viral diseases will certainly brighten the prospects of plant virus control in the coming decades.</jats:p